<!DOCTYPE HTML>
<html>
<head>
  <style>
    table {
      border-collapse: collapse;
    }

    td {
      border: 1px solid black;
      padding: 3px 5px;
    }
  </style>
</head>

<body>
<table>
  <tr>
    <td style="background-color: red;">1:1</td>
    <td>2:1</td>
    <td>3:1</td>
    <td>4:1</td>
    <td>5:1</td>
  </tr>
  <tr>
    <td>1:2</td>
    <td style="background-color: red;">2:2</td>
    <td>3:2</td>
    <td>4:2</td>
    <td>5:2</td>
  </tr>
  <tr>
    <td>1:3</td>
    <td>2:3</td>
    <td style="background-color: red;">3:3</td>
    <td>4:3</td>
    <td>5:3</td>
  </tr>
  <tr>
    <td>1:4</td>
    <td>2:4</td>
    <td>3:4</td>
    <td style="background-color: red;">4:4</td>
    <td>5:4</td>
  </tr>
  <tr>
    <td>1:5</td>
    <td>2:5</td>
    <td>3:5</td>
    <td>4:5</td>
    <td style="background-color: red;">5:5</td>
  </tr>
</table>
</body>
</html>
